如何在嵌套列表上保存循环的输出

Question

我有一个嵌套数据框列表：

set.seed(1)
S1 = data.frame(replicate(2,sample(0:130,30,rep=TRUE)))
S2 = data.frame(replicate(2,sample(0:130,34,rep=TRUE)))
S3 = data.frame(replicate(2,sample(0:130,21,rep=TRUE)))
S4 = data.frame(replicate(2,sample(0:130,26,rep=TRUE)))
df_list1 = list(S1 = S1, S2 = S2, S3 = S3, S4 = S4)

set.seed(2)
S1 = data.frame(replicate(2,sample(0:130,30,rep=TRUE)))
S2 = data.frame(replicate(2,sample(0:130,34,rep=TRUE)))
S3 = data.frame(replicate(2,sample(0:130,21,rep=TRUE)))
S4 = data.frame(replicate(2,sample(0:130,26,rep=TRUE)))
df_list2 = list(S1 = S1, S2 = S2, S3 = S3, S4 = S4)

set.seed(3)
S1 = data.frame(replicate(2,sample(0:130,30,rep=TRUE)))
S2 = data.frame(replicate(2,sample(0:130,34,rep=TRUE)))
S3 = data.frame(replicate(2,sample(0:130,21,rep=TRUE)))
S4 = data.frame(replicate(2,sample(0:130,26,rep=TRUE)))
df_list3 = list(S1 = S1, S2 = S2, S3 = S3, S4 = S4)

set.seed(4)
S1 = data.frame(replicate(2,sample(0:130,30,rep=TRUE)))
S2 = data.frame(replicate(2,sample(0:130,34,rep=TRUE)))
S3 = data.frame(replicate(2,sample(0:130,21,rep=TRUE)))
S4 = data.frame(replicate(2,sample(0:130,26,rep=TRUE)))
df_list4 = list(S1 = S1, S2 = S2, S3 = S3, S4 = S4)

df_list = list (df_list1, df_list2, df_list3, df_list4)
names(df_list) = c("AB_df", "BC_df", "DE_df", "FG_df")

我想通过循环提取每个数据帧的第一列并将其保存到列表中。我现在的问题是如何使循环正确保存。我必须使用哪个运行索引？我尝试了不同的版本，但没有任何效果。这是我的代码，我现在需要知道用什么来代替???

datalist = list()
for (a in 1:length(df_list)) {
  for (b in 1:length(df_list[[1]])) {
    datalist[[?????]] = df_list[[a]][[b]][1]}}

为了更清楚：作为输出，我想要一个包含所有 16 个数据帧的每一列的列表。所以 16 个列表条目。

Answer 1

purrr 在这里完美运行。

library(purrr)

datalist <-
  df_list %>% 
  # prepend top level names to dataframe names
  imap(~ set_names(.x, function(nms) {paste(.y, nms, sep = "-")})) %>% 
  flatten() %>% 
  map(1)